Three directors received credit for Sin City: Miller, Rodriguez and Quentin Tarantino the latter for directing one scene in the film. Miller and Rodriguez worked as a team directing the rest of the film. Despite having no previous directorial background, Miller was substantially involved in the direction of the film, providing direction to the actors on their motivations and what they needed to bring to each scene. Because of this (and the fact that Miller's original books were used as storyboards), Rodriguez felt that they should both be credited as directors on the film.
When the Director's Guild of America refused to allow two directors that were not an established team to be credited (especially since Miller had never directed before), Rodriguez first planned to give Miller full credit. Miller would not accept this, as he certainly could not have done it without Rodriguez. Rodriguez, also refusing to take full credit, decided to resign from the Guild so that the joint credit could remain.